CVE-2026-21870 – The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokenizer_string

CVE ID : CVE-2026-21870

Published : Feb. 13, 2026, 5:58 p.m. | 31 minutes ago

Description : BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow.

Severity: 0.0 | NA

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